Tobacco is an example of one agricultural material that is cultivated and harvested. Harvested tobacco leaves have a relatively high water content and thus cannot be used directly to manufacture a commercial tobacco product. For this reason, the harvested tobacco leaves are dried so as to remove moisture therefrom. In general, therefore, only dried tobacco leaves may be preserved or used to manufacture a commercial tobacco product.
Tobacco leaves however, shrink extremely when they are dried. The tobacco material manufactured from such dried tobacco leaves also experiences shrinkage (i.e. reduction in volume). If tobacco material of reduced volume is used to manufacture cigarettes, for example, the amount of tobacco material per cigarette must be increased thereby deleteriously affecting cigarette productivity.
Due to the above circumstances, therefore, the dried tobacco material is expanded to increase the volume of the tobacco material, prior to use of the tobacco material to manufacture cigarettes, thereby improving cigarette productivity.
Conventional apparatus for expanding tobacco material are described in Japanese Patent Publication No. 49-1879 and Japanese Patent Disclosure (Kokai) No. 50-107197. The apparatus described in Japanese Publication No. 49-1879 includes an impregnation vessel used to impregnate the tobacco material with an organic solvent. More specifically, organic solvent is separated into liquid and gaseous phases. The tobacco material in the impregnation vessel is first dipped in the liquid-phase organic solvent, and then subsequently is contacted with the gaseous-phase organic solvent. The tobacco material impregnated with organic solvent is removed from the impregnation vessel and is heated. Upon heating, organic solvent contained in the impregnated tobacco material is evaporated as a gas from the tobacco material. By the evaporation of organic solvent, the tobacco material is expanded.
In the apparatus disclosed in Japanese Patent Disclosure (Kokai) No. 50-107197, liquefied carbon dioxide is used as an expanding agent in order to expand the tobacco material. In the expanding apparatus disclosed in Japanese Patent Publication No. 50-107197 the principle of expanding the tobacco material is the same as that in Japanese Patent Publication No. 49-1879 discussed above. In this regard, tobacco material impregnated with carbon dioxide is heated to evaporate carbon dioxide gas from the tobacco material, and thereby expand the tobacco material.
Since the expanding apparatus disclosed in Japanese Patent Publication No. 49-1879 uses liquefied organic solvent as an expanding agent, the internal pressure of the impregnation vessel required to impregnate the tobacco material with organic solvent can be relatively low. In such a apparatus using liquefied organic solvent, the tobacco material can be charged continuously in the impregnation vessel so as to impregnate the tobacco material with organic solvent, and thus expansion of the tobacco material can be continuously performed.
Freon.TM. halogenated hydrocarbons are conventionally used as expanding agents. However, since Freon.TM.hydrocarbons are a known environmental pollutant, the amount of Freon.TM. hydrocarbon production has recently been decreased, with the result being that the cost of Freon.TM. has increased. For this reason, when an expanding apparatus using Freon.TM. hydrocarbon is employed in the tobacco production line, the cost of such tobacco is inevitably increased with an increase in the cost of the Freon.TM. hydrocarbons.
The expanding apparatus described in Japanese Patent Disclosure (Kokai) No. 50-107197 uses liquefied carbon dioxide in place of Freon.TM. halogenated hydrocarbons as an expanding agent. Although the disadvantages of Freon.TM. can be eliminated, the advantage thereof (i.e., a continuous treatment) is lost. When carbon dioxide as an expanding agent is used to impregnate the tobacco material to a desired level, the internal pressure of the impregnation vessel (i.e., the pressure of carbon dioxide) must be kept at a high pressure regardless of the liquid- and gaseous-phase carbon dioxide. For this reason, in expanding apparatus using carbon dioxide, the internal pressure of the impregnation vessel must be kept at a high pressure. In addition, the tobacco material to be expanded cannot be continuously charged into the impregnation vessel. As a result, in the expanding apparatus using carbon dioxide, the expansion treatment is inevitably a batch process. Therefore, such an apparatus is not suitable for expanding a large amount of tobacco material. When carbon dioxide is used as an expanding agent, the amount of carbon dioxide impregnated in the tobacco material is relatively small. For this reason, the tobacco material impregnated with carbon dioxide must be immediately heated, preferably within two minutes. Otherwise, desired expansion of the tobacco material cannot be achieved. Under these circumstances, it is difficult to use the batch type expanding apparatus using carbon dioxide as an expanding agent in practical (i.e., industrial) applications.
When liquefied dioxide is used as an expanding agent, a large amount of dry ice is contained in the tobacco material removed from the impregnation vessel to the outer atmosphere. For this reason, a large amount of liquefied carbon dioxide is lost. The amount of carbon dioxide supplied to the impregnation vessel (i.e. the amount of carbon dioxide used) is inevitably increased. In addition, the tobacco material must be heated at a higher temperature during heating of the tobacco material.
It is an object of the present invention to provide an apparatus for expanding materials of agricultural origin, such as foodstuffs, and the like to be expanded, wherein carbon dioxide can be properly used as an impregnating agent, i.e., an expanding agent, and expansion of the material can be performed continuously.
In order to achieve the above object of the present invention, there is provided an apparatus for expanding material of agricultural origin, comprising a preparatory vessel which receives the material and is open to the outer atmosphere. Air in the preparatory vessel is substituted with a gaseous impregnating agent supplied from an impregnating agent source. The material in the preparatory vessel is introduced into an impregnation vessel through a convey pipe. An impregnating agent having a pressure higher than atmospheric pressure is supplied from the impregnating agent source so that the impregnation vessel is filled with the impregnating agent.
The expanding apparatus also comprises booster means for filling the impregnating agent in the convey pipe and boosting the pressure of the impregnating agent around the material to a pressure substantially equal to that in the impregnation vessel immediately before the supply of the material from the convey pip to the impregnation vessel, while the pressure in the impregnation vessel is kept unchanged.
One end of a delivery pipe is connected to the impregnation vessel to discharge the material impregnated with the impregnating agent in the impregnation vessel. The other end of the delivery pipe is connected to a blow pipe for conveying the impregnated material with air. A flow of a heating medium heated to a predetermined temperature is generated in the blow pipe.
The expanding apparatus also comprises a debooster means having a function opposite to that of the booster means. The debooster means fills the impregnating agent from the impregnating agent source in the delivery pipe and reduces the pressure of the impregnating agent around the impregnated material to a pressure substantially equal to that of the blow pipe, immediately before delivery of the impregnated material from the delivery pipe to the blow pipe, while the pressure of the impregnation vessel is kept unchanged.
According to the expanding apparatus of the present invention, the material is charged in the impregnation vessel from the preparatory vessel through the convey pipe and is impregnated in the impregnation vessel. The impregnated material is discharged from the impregnation vessel to the blow pipe through the delivery pipe. The impregnated material discharged in the blow pipe is heated by the heating medium flowing in the blow pipe while being conveyed by the flow of the heating medium. During blowing, the impregnated material is expanded. That is, the agent impregnated in the material is evaporated by heating of the material, and evaporation of the impregnating agent allows expansion of the material.
According to the expanding apparatus of the present invention as described above, the booster means is arranged to supply the material from the preparatory vessel to the impregnation vessel through the convey pipe, and the debooster means is arranged to discharge the impregnated material from the impregnation vessel to the blow pipe through the delivery pipe. Therefore, the material can be continuously supplied to the impregnation vessel or discharged therefrom while the pressure of the impregnation vessel is kept unchanged. Therefore, impregnation of the material can be continuously performed, and expansion of the impregnated material can also be continuously performed.
The pressure of the impregnation vessel can be kept unchanged although continuous impregnation in the impregnation vessel is performed. Therefore, carbon dioxide which requires a high impregnation pressure can be used as an impregnating agent.